1. Field of the Invention
The present invention relates in general to automated manual transmissions, viz., automotive manual transmissions of an automatic speed change type that includes a plurality of shift forks, a first clutch used for establishing odd number speeds, a second clutch used for establishing even number speeds and a plurality of hydraulic shift actuators for actuating the shift forks respectively. More specifically, the present invention is concerned with a shift position sensor of such automated manual transmissions, which senses a shift position that is actually taken by the transmission.
2. Description of the Related Art
In order to clarify the task of the present invention, one known automated manual transmission will be briefly described, which is disclosed in Japanese Laid-open Patent Application (Tokkaihei) 8-320054.
The transmission disclosed in the Patent Application is of a twin clutch type that comprises a first clutch for a first group of gears that are arranged for establishing odd number speeds and a second clutch for a second group of gears that are arranged for establishing even number speeds. In such transmission, under a condition wherein one speed is selected by the gears of the first group (or second group) with the first clutch (or second clutch) kept engaged, no speed can be established by the gears of the second group (or first group). While, when, upon need of a speed change, one gear of the second group (or first group) is selected by a synchronizing meshing mechanism with the second clutch (or first clutch) kept disengaged, the first clutch (or second clutch) is disengaged and then the second clutch (or first clutch) is engaged. That is, in such transmission, a so-called automatic speed change is carried out by controlling the alternative selection of gears between the first and second groups of gears as well as the switching between first and second clutches.
In order to provide the transmission of the above-mentioned twin clutch type with such automatic speed change, there is a need of feeding a control unit of the transmission with information on the speed that is actually taken by the transmission.
In order to get such information, some of known transmissions employ a shift position sensor that comprises generally two magnets mounted on each shift fork or shift rod through a sensor bracket and a magnaflux detector mounted to an inner wall of a transmission case at a position near the two magnets. That is, when, upon a shift change operation by a driver, a corresponding shift fork or shift rod is moved together with the two magnets mounted thereon, an inevitable change of the magnaflux is sensed by the magnaflux detector, which provides the control unit with the information on change of the speed.